U.S. patent application number 17/578453 was filed with the patent office on 2022-05-05 for cache management in a printing system in a virtualized computing environment.
This patent application is currently assigned to VMware, Inc.. The applicant listed for this patent is VMware, Inc.. Invention is credited to Qi AN, Weigang HUANG, Mangui SHE, Kun SHI, Hui YUAN, Hui ZHANG.
Application Number | 20220137905 17/578453 |
Document ID | / |
Family ID | 1000006090513 |
Filed Date | 2022-05-05 |
United States Patent
Application |
20220137905 |
Kind Code |
A1 |
YUAN; Hui ; et al. |
May 5, 2022 |
CACHE MANAGEMENT IN A PRINTING SYSTEM IN A VIRTUALIZED COMPUTING
ENVIRONMENT
Abstract
A varied least recently used (VLRU) caching technique is used to
enable print data to be available at a cache of a client for
printing, even after an agent performs a deletion of a hash value
for the print data at a cache of the agent. The deletion of the
print data (cached at the cache of the client) is postponed at the
client device via the use of a waiting list, so that the cached
print data can be printed at a physical printer of the client, in
response to receiving a delayed print job from the agent that
specifies the hash value as a result of a deduplication process
performed by the agent.
Inventors: |
YUAN; Hui; (Beijing, CN)
; HUANG; Weigang; (Beijing, CN) ; SHE; Mangui;
(Beijing, CN) ; AN; Qi; (Beijing, CN) ;
ZHANG; Hui; (Beijing, CN) ; SHI; Kun;
(Beijing, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VMware, Inc. |
Palo Alto |
CA |
US |
|
|
Assignee: |
VMware, Inc.
Palo Alto
CA
|
Family ID: |
1000006090513 |
Appl. No.: |
17/578453 |
Filed: |
January 19, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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17084641 |
Oct 30, 2020 |
11262960 |
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17578453 |
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Current U.S.
Class: |
358/1.16 |
Current CPC
Class: |
G06F 12/122 20130101;
G06F 3/1274 20130101; G06F 12/123 20130101; G06F 3/122 20130101;
G06F 3/1263 20130101; G06F 3/1259 20130101; G06F 2212/1021
20130101; G06F 3/1205 20130101 |
International
Class: |
G06F 3/12 20060101
G06F003/12; G06F 12/123 20060101 G06F012/123; G06F 12/122 20060101
G06F012/122 |
Claims
1. A method performed by an agent to issue print jobs for print
data to be printed by a client, the method comprising: generating a
first print job having a first data structure that includes a hash
value corresponding to first print data at a cache node at the
client, wherein the first data structure indicates that a
deduplication condition exists for the first print data; sending
the first print job to the client; generating a second print job
having a second data structure that specifies a hit count for the
hash value and a delete operation to be performed for the first
print data at the cache node; and sending the second print job to
the client, after sending the first print job to the client,
wherein the client receives the second print job from the agent
before receiving the first print job, and postpones, based at least
in part on the hit count, execution of the delete operation
specified by the second data structure in the second print job.
2. The method of claim 1, wherein in response to receiving the
first print job and based at least in part on the hash value and
the hit count, the client locates the first print data at the cache
node, sends the located first print data to a physical printer for
printing, and executes the delete operation to delete the first
print data from the cache node after completion of the
printing.
3. The method of claim 1, further comprising: hashing new print
data at the agent to obtain a particular hash value; determining
that a match exists between the new hash value and the hash value
corresponding to the first print data; and in response to
determination that the match exists, incrementing the hit count by
one.
4. The method of claim 1, wherein sending the first print job to
the client, under the deduplication condition, includes sending
only the hash value without sending the first print data to the
client.
5. The method of claim 1, wherein: generating the second print job
includes generating the second data structure to include, in
addition to specifying the hit count for the hash value and the
delete operation, second print data, a hash value corresponding to
the second print data, and an indication that the second print data
is to be added to the cache at the client; and sending the second
print job includes sending, to the client, the generated second
data structure that includes the second print data, the hash value
corresponding to the second print data, and the indication that the
second print data is to be added to the cache at the client.
6. The method of claim 1, wherein the client postpones execution of
the delete operation in response to the hit count specified in the
second data structure being different than a hit count for the
first print data at the cache node.
7. The method of claim 1, wherein the agent is associated with a
virtual desktop and with a virtual printer that is an instantiation
of a physical printer of the client.
8. A computing device, comprising: a processor associated with an
agent; and a non-transitory computer-readable medium coupled to the
processor and having instructions stored thereon, which in response
to execution by the processor, cause the agent to perform
operations to issue print jobs for print data to be printed by a
client, wherein the operations comprise: generate a first print job
having a first data structure that includes a hash value
corresponding to first print data at a cache node at the client,
wherein the first data structure indicates that a deduplication
condition exists for the first print data; send the first print job
to the client; generate a second print job having a second data
structure that specifies a hit count for the hash value and a
delete operation to be performed for the first print data at the
cache node; and send the second print job to the client, after
sending the first print job to the client, wherein the client
receives the second print job from the agent before receiving the
first print job, and postpones, based at least in part on the hit
count, execution of the delete operation specified by the second
data structure in the second print job.
9. The computing device of claim 8, wherein in response to
receiving the first print job and based at least in part on the
hash value and the hit count, the client locates the first print
data at the cache node, sends the located first print data to a
physical printer for printing, and executes the delete operation to
delete the first print data from the cache node after completion of
the printing.
10. The computing device of claim 8, wherein the operations further
comprise: hash new print data at the agent to obtain a particular
hash value; determine that a match exists between the new hash
value and the hash value corresponding to the first print data; and
in response to determination that the match exists, increment the
hit count by one.
11. The computing device of claim 8, wherein the operations to send
the first print job to the client, under the deduplication
condition, includes operations to send only the hash value without
sending the first print data to the client.
12. The computing device of claim 8, wherein: the operations to
generate the second print job includes operations to generate the
second data structure to include, in addition to specifying the hit
count for the hash value and the delete operation, second print
data, a hash value corresponding to the second print data, and an
indication that the second print data is to be added to the cache
at the client; and the operations to send the second print job
includes operations to send, to the client, the generated second
data structure that includes the second print data, the hash value
corresponding to the second print data, and the indication that the
second print data is to be added to the cache at the client.
13. The computing device of claim 8, wherein the client postpones
execution of the delete operation in response to the hit count
specified in the second data structure being different than a hit
count for the first print data at the cache node.
14. The computing device of claim 8, wherein the agent is
associated with a virtual desktop and with a virtual printer that
is an instantiation of a physical printer of the client.
15. A method performed by a client to process print jobs that
originate from an agent, the method comprising: receiving a print
job having a data structure generated by the agent, wherein the
data structure specifies a delete operation to be performed for
print data at a cache node at a cache at the client, and wherein
the data structure further specifies a hit count for a hash value
corresponding to the print data at the cache node; reading the data
structure in the print job; and in response to determining that the
received data structure specifies the delete operation and based at
least in part on the hit count, postponing deletion of the print
data from the cache node by storing the hash value in a waiting
list at the client.
16. The method of claim 15, wherein the client postpones deletion
of the print data in response to the hit count specified in the
data structure being different than a hit count for the print data
at the cache node.
17. The method of claim 15, further comprising: receiving another
print job that is out-of-sequence in time relative to the print
job, wherein the another print job has another data structure
generated by the agent, and wherein the another data structure
indicates that a deduplication condition exists for the print data
corresponding to the hash value; and in response to determining
that the another data structure indicates the deduplication
condition: locating the print data in the cache node using the hash
value; sending the located print data to a physical printer for
printing; and after completion of the printing, executing the
delete operation to delete the print data from the cache node.
18. The method of claim 17, wherein the another data structure
includes the hash value and omits the print data.
19. The method of claim 15, wherein the print data comprises first
print data, and wherein the method further comprises: receiving
another print job that has another data structure generated by the
agent, wherein the another data structure includes second print
data, a hash value corresponding to the second print data, and an
indication that the second print data is to be added to the cache
at the client; and adding the second print data to the cache.
20. The method of claim 15, wherein the print data comprises first
print data, and wherein the data structure, which specifies the hit
count for the hash value and the delete operation, further
includes: second print data, a hash value corresponding to the
second print data, and an indication that the second print data is
to be added to the cache at the client.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation application under
35 U.S.C. .sctn. 120 of U.S. patent application Ser. No.
17/084,641, filed Oct. 30, 2020, which is incorporated herein by
reference in its entirety.
BACKGROUND
[0002] Unless otherwise indicated herein, the approaches described
in this section are not admitted to be prior art by inclusion in
this section.
[0003] Virtualization allows the abstraction and pooling of
hardware resources to support virtual machines in a
software-defined networking (SDN) environment, such as a
software-defined data center (SDDC). For example, through server
virtualization, virtualized computing instances such as virtual
machines (VMs) running different operating systems (OSs) may be
supported by the same physical machine (e.g., referred to as a
host). Each virtual machine is generally provisioned with virtual
resources to run an operating system and applications. The virtual
resources in a virtualized computing environment may include
central processing unit (CPU) resources, memory resources, storage
resources, network resources, etc.
[0004] One example use of a virtualized computing environment is
for a virtual desktop infrastructure (VDI) implementation, which is
a type of desktop virtualization that allows a desktop to run on
VMs that are provided by a hypervisor on a host. A user/client uses
the operating system (OS) and applications (which reside and
execute at the VM) via an endpoint device of the user, just as if
the OS/applications were actually running locally on the endpoint
device.
[0005] VDI implementations provide the user with printing
capability, so that the user can issue print jobs from the virtual
desktop at the VM, and then the printing is performed at a physical
printer that is connected to the user's endpoint device (client
device). However, printing in a virtualized computing environment
(such as one that is implementing VDI) is prone to caching
limitations and errors, which may result in failed print jobs at
the physical printer of the client device.
BRIEF DESCRIPTION OF DRAWINGS
[0006] FIG. 1 is a schematic diagram illustrating an example
virtualized computing environment that can implement a VDI with
printing capability;
[0007] FIG. 2 is a diagram illustrating client and agent devices
and printers for the virtualized computing environment of FIG.
1;
[0008] FIG. 3 is a diagram illustrating an example of a least
recently used (LRU) caching technique for a printing process;
[0009] FIG. 4 is a diagram illustrating a further example of the
LRU caching technique for a printing process;
[0010] FIG. 5 is a diagram illustrating an example of a varied LRU
(VLRU) caching technique for a printing process for the client and
agent devices and printers of FIG. 2;
[0011] FIG. 6 is a diagram illustrating a further example of the
VLRU caching technique for a printing process for the client and
agent devices and printers of FIG. 2;
[0012] FIG. 7 is a diagram illustrating another example of the VLRU
caching technique for a printing process for the client and agent
devices and printers of FIG. 2;
[0013] FIG. 8 is flowchart of an example method to perform the VLRU
caching technique in the virtualized computing environment of FIG.
1; and
[0014] FIG. 9 is a flowchart of an example method associated with
an updating node (deduplication) for the VLRU caching technique of
FIG. 8;
[0015] FIG. 10 is a flowchart of an example method associated with
an adding node for the VLRU caching technique of FIG. 8; and
[0016] FIG. 11 is a flowchart of an example method associated with
a deleting node for the VLRU caching technique of FIG. 8.
DETAILED DESCRIPTION
[0017] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof. In the
drawings, similar symbols typically identify similar components,
unless context dictates otherwise. The illustrative embodiments
described in the detailed description, drawings, and claims are not
meant to be limiting. Other embodiments may be utilized, and other
changes may be made, without departing from the spirit or scope of
the subject matter presented here. The aspects of the present
disclosure, as generally described herein, and illustrated in the
drawings, can be arranged, substituted, combined, and designed in a
wide variety of different configurations, all of which are
explicitly contemplated herein.
[0018] References in the specification to "one embodiment", "an
embodiment", "an example embodiment", etc., indicate that the
embodiment described may include a particular feature, structure,
or characteristic, but every embodiment may not necessarily include
the particular feature, structure, or characteristic. Moreover,
such phrases are not necessarily referring to the same embodiment.
Further, when a particular feature, structure, or characteristic is
described in connection with an embodiment, such feature,
structure, or characteristic may be effected in connection with
other embodiments whether or not explicitly described.
[0019] The present disclosure addresses drawbacks when executing
print jobs from virtual desktops in virtualized computing
environments. A caching method, referred to herein as a varied
least recently used (VLRU) caching method, implements adding,
deleting, and updating operations for a printer cache and reduces
the chances of losing cached data at a client side when
deduplication is performed at an agent side for the update
operation.
[0020] Computing Environment
[0021] To further explain the details of the VLRU method and how
the VLRU method improves the printing process in a virtual desktop
infrastructure (VDI) or other type of virtual desktop environment,
reference is first made herein to FIG. 1, which is a schematic
diagram illustrating an example virtualized computing environment
100 that can implement VDI with printing capability. Depending on
the desired implementation, virtualized computing environment 100
may include additional and/or alternative components than that
shown in FIG. 1.
[0022] In the example in FIG. 1, the virtualized computing
environment 100 includes multiple hosts, such as host-A 110A . . .
host-N 110N that may be inter-connected via a physical network 112,
such as represented in FIG. 1 by interconnecting arrows between the
physical network 112 and host-A 110A . . . host-N 110N. Examples of
the physical network 112 can include a wired network, a wireless
network, the Internet, or other network types and also combinations
of different networks and network types. For simplicity of
explanation, the various components and features of the hosts will
be described hereinafter in the context of the host-A 110A. Each of
the other host-N 110N can include substantially similar elements
and features.
[0023] The host-A 110A includes suitable hardware 114A and
virtualization software (e.g., a hypervisor-A 116A) to support
various virtual machines (VMs). For example, the host-A 110A
supports VM1 118 . . . VMX 120. In practice, the virtualized
computing environment 100 may include any number of hosts (also
known as computing devices, host computers, host devices, physical
servers, server systems, physical machines, etc.), wherein each
host may be supporting tens or hundreds of virtual machines. For
the sake of simplicity, the details of only the single VM1 118 are
shown and described herein.
[0024] VM1 118 may be an agent-side VM that includes a guest
operating system (OS) 122 and one or more guest applications 124
(and their corresponding processes) that run on top of the guest OS
122. Using the guest OS 122 and/or other resources of VM1 118 and
the host-A 110A, VM1 118 may generate a virtual desktop 126 that is
operated by and accessible to one or more client-side user
device(s) 146 via the physical network 112. One or more virtual
printers 128 may be instantiated in VM1 118 and/or elsewhere in the
host-A 110A. VM1 118 may include other elements, such as code and
related data (including data structures), engines, etc., which will
not be explained herein in further detail, for the sake of brevity.
The user device 146 may include printer tools 148 (explained in
more detail in FIG. 2) to support print jobs at physical printers
that are locally connected to the user device 146.
[0025] The hypervisor-A 116A may be a software layer or component
that supports the execution of multiple virtualized computing
instances. The hypervisor-A 116A may run on top of a host operating
system (not shown) of the host-A 110A or may run directly on
hardware 114A. The hypervisor 116A maintains a mapping between
underlying hardware 114A and virtual resources (depicted as virtual
hardware 130) allocated to VM1 118 and the other VMs. The
hypervisor-A 116A may include other elements (shown generally at
140), including tools to support print jobs that are issued by VM1
118 to the virtual printers 128 and various other tools to provide
resources for and to otherwise support the operation of the
VMs.
[0026] Hardware 114A in turn includes suitable physical components,
such as central processing unit(s) (CPU(s)) or processor(s) 132A;
storage device(s) 134A; and other hardware 136A such as physical
network interface controllers (NICs), storage disk(s) accessible
via storage controller(s), etc. Virtual resources (e.g., the
virtual hardware 130) are allocated to each virtual machine to
support a guest operating system (OS) and application(s) in the
virtual machine, such as the guest OS 122 and the application(s)
124 (e.g., a word processing application, accounting software, a
browser, etc.) in VM1 118. Corresponding to the hardware 114A, the
virtual hardware 130 may include a virtual CPU, a virtual memory
(including agent-side caches used for print jobs for the virtual
printers 128), a virtual disk, a virtual network interface
controller (VNIC), etc.
[0027] The management server 142 of one embodiment can take the
form of a physical computer with functionality to manage or
otherwise control the operation of host-A 110A . . . host-N 110N.
In some embodiments, the functionality of the management server 142
can be implemented in a virtual appliance, for example in the form
of a single-purpose VM that may be run on one of the hosts in a
cluster or on a host that is not in the cluster.
[0028] The management server 142 may be communicatively coupled to
host-A 110A . . . host-N 110N (and hence communicatively coupled to
the virtual machines, hypervisors, hardware, etc.) via the physical
network 112. In some embodiments, the functionality of the
management server 142 may be implemented in any of host-A 110A . .
. host-N 110N, instead of being provided as a separate standalone
device such as depicted in FIG. 1.
[0029] Depending on various implementations, one or more of the
physical network 112, the management server 142, and the user
device(s) 146 can comprise parts of the virtualized computing
environment 100, or one or more of these elements can be external
to the virtualized computing environment 100 and configured to be
communicatively coupled to the virtualized computing environment
100.
[0030] FIG. 2 is a diagram illustrating client and agent devices
and printers for the virtualized computing environment 100 of FIG.
1. More specifically, FIG. 2 shows the client (e.g., the user
device 146), the agent (e.g., the VM1 118 that provides the virtual
desktop 126), and their associated elements and printers that
execute print jobs.
[0031] At the client side, the user device 146 is connected (via a
network, universal serial bus (USB), or other wired/wireless
connection) to a plurality of physical printers 200. The physical
printers 200 include, for instance, a printer-A 202, a printer-B
204, and a printer-C 206. The user device 146 access, operates, or
otherwise communicates with the virtual desktop 126 running on VM1
118 at the agent side, via a VDI connection 208 provided by the
physical network 112.
[0032] The printer tools 148 of the user device 146 include a
printer redirection client 210 along with a client cache system 212
as a sub-component. The printer tools 148 also include a print
helper 214 and spooler service(s) 216 that operate in conjunction
with the printer redirection client 210 and the client cache system
212 to prepare and send (shown at 218) print data for print jobs to
the printers 200.
[0033] Correspondingly installed at the agent side is a printer
redirection server 220 along with an agent cache system 222 as a
sub-component, a print processor 224, and spooler service(s) 226
that operate in conjunction with the printer redirection server 220
and the agent cache system 222 to prepare and send (shown at 228)
print data to the printer redirection client 210 for printing at
the printers 200. One or more of the printer redirection server
220, the agent cache system 222, the print processor 224, and the
spooler service(s) 226 can reside at VM1 118 or elsewhere in the
host-A 110A.
[0034] When the VDI connection 208 is established between the
client and the agent, information regarding the printers 200 is
sent (shown at 230) from the printer redirection client 210 to the
printer redirection server 220 via the VDI connection 208. This
information is used by the printer redirection server 220 to
instantiate the virtual printers 128. Thus, the virtual printers
128 include a virtual printer-A 232, a virtual printer-B 234, and a
virtual printer-C 236 that respectively represent the physical
printer-A 202, printer-B 204, and printer-C 206.
[0035] In operation, when the virtual desktop 126 issues a print
job for one of the virtual printers (for instance, the virtual
printer-C 236), the print processor 224 gets the print data from
the spooler service(s) 226 and converts the print data to an
appropriate format, and sends the print data to the agent cache
system 222 so that the printer redirection server 220 can then
transfer (at 228) the print data to the printer redirection client
210 at the client side. When the client cache system 212 receives
the print data, the client cache system 212 sends the print data to
the print helper 214. The print helper 214 will then write, via the
spooler service(s) 216, the print data to the printer-C 206 for
printing.
[0036] The above-described process involves a situation when the
to-be-printed print data is new data, and so the print data itself
is transferred from the agent side to the client side. However, in
other situations, frequently used print data may need to be
printed, and it is inefficient for the agent side to repeatedly
send the same print data again to the client side. Therefore, some
implementations use deduplication and hashing techniques in
conjunction with caching, in order to advantageously reduce the
amount of data transfer from the agent side to the client side, and
thus provide more efficient and improved performance and better
bandwidth utilization.
[0037] Specifically, at the agent side, the print data from the
virtual desktop 126 is hashed (e.g., via MD5 or other hashing
algorithm) by the printer redirection server 220 or some other
component at the agent side, so as to generate a hash value or
other fingerprint that uniquely identifies the print data. If the
print data is new data, then the agent side sends the hash value
and the actual print data to the client side. The agent side also
stores the hash value (and not the actual print data) in the agent
cache system 222, and the client side in turn stores both the hash
value and the actual print data in the client side cache system
212.
[0038] On the other hand, if the print data received from the
virtual desktop 126 is a repeat copy of previous data, the agent
side should try to avoid resending that same/repeated data.
Accordingly, deduplication is performed in which the printer
redirection server 220 determines whether a hash value of the
received print data matches a hash value that is currently stored
in the agent cache system 222. If a matching hash value is found in
the agent cache system 222, which indicates to the printer
redirection server 220 that the corresponding print data is also
cached at the client cache system 212, then the printer redirection
server 220 need only send the hash value (and not send the
repeat/duplicate of the print data) to the printer redirection
client 210, so that the printer redirection client 210 can use that
hash value to locate the corresponding print data in the client
cache system 212 for printing.
[0039] In order for the above-described caching, hashing, and
deduplication process to work properly, there are some
configuration/operational requirements. First, the contents of the
agent cache system 222 and the contents of the client cache system
212 need to maintain consistency/coherency with each other. That
is, when deduplication is performed wherein the agent side finds
the hash value of the print data in the agent cache system 222 and
therefore sends the hash value of the print data (and not the
actual print data) to the client side, the agent side is assuming
that both caches are consistent with each other in that the
corresponding print data is still cached at the client side and
thus can be located/restored for printing. Thus, cache
coherency/consistency requires that if a hash value is still cached
at the agent side, the corresponding print data must also still be
cached at the client side.
[0040] Second, caches have a maximum size limit (e.g., when a cache
is full, cache entries will need to be removed in order to add new
cache entries). Accordingly, cache management becomes an important
consideration when adding to or removing from a cache in order to
operate within the size limits of the caches, and at the same time,
maintaining cache coherency/consistency between the caches at the
agent side and client side such that printing can be successfully
performed when deduplication is involved.
[0041] Some printing systems use a least recently used (LRU)
caching technique in conjunction with performing the
above-described processes of caching, hashing, and deduplication.
The entries in the caches are organized as rows in a cache list,
with each row in the cache list being referred to as a cache node.
Thus, a hash value and its corresponding print data represent a
single cache node. FIG. 3 is an example of one such LRU caching
technique 300 for a printing process, and more particularly, FIG. 3
(as well as FIG. 4 thereafter) shows some of the drawbacks
associated with the use of the LRU caching technique 300 for
printing.
[0042] In FIG. 3, an agent cache system 302 just needs to cache (a)
the fingerprints (hash values H.sub.1 . . . H.sub.N) for the print
data that is cached at a client cache system 304 and (b) the
corresponding data size (S.sub.1 . . . S.sub.N). The client cache
system 304, in addition to storing the fingerprints and data sizes,
also stores the corresponding actual print data (A, B, . . . X) for
printing and for later restoring deduped print data.
[0043] One cache row (cache node) of each cache system denotes one
record in a cache list, which is organized like a queue in each
cache system. Thus, when new data is being inserted into the cache
list, the new data will be placed at the front node of the queue,
and as each subsequent new data is placed into the cache list, the
previously inserted data is moved from the front node towards the
rear node of the queue. This process repeats until the queue/cache
is full, such that when new data is to be inserted at the front
node of the full cache, the data at the rear node of the cache is
removed (e.g., is flushed out or deleted).
[0044] For new print data that has not yet been cached at the
client cache system 304, the agent cache system 302 generates and
sends a data structure {hash_value [data_size, data]} to the client
cache system 304, with the brackets [ ] indicating that the
data_size and data are unnecessary in a deduplication scenario.
When deduplication is involved such that the agent cache system 302
determines that the same hash value is still cached at the agent
side, the agent cache system 302 sends only the fingerprint in a
data structure {hash_value} to the client cache system 304 instead
of the actual print data, since the actual print data has already
been previously sent to the client cache system 302. Thereafter,
when the client cache system 304 receives the fingerprint (hash
value), the client cache system 304 will use the hash value to try
to restore/locate the previously cached print data, and send that
print data to a print helper for printing at a physical
printer.
[0045] As shown in FIG. 3, there is a specific sequence for the
records in the queue at the agent cache system 302 (e.g., H.sub.1,
H.sub.2, . . . H.sub.N), which represents an order of execution of
respective print jobs for print data A, B, . . . X. However, due to
network latency in the VDI connection 306 between the agent cache
system 302 and the client cache system 304, there is no guarantee
that the same sequence will be present in the client cache system
302. For example, FIG. 3 shows that the sequence H.sub.2, H.sub.1,
. . . H.sub.N (B, A, . . . X) in the client cache system 304 is now
mismatched with the sequence in the agent cache system 302.
[0046] FIG. 4 is a diagram illustrating a further example of the
LRU caching technique for a printing process. More specifically,
FIG. 4 shows how mismatched sequences at the agent cache system 302
and client cache system 304 results in failed print jobs when using
the LRU technique.
[0047] In the example of FIG. 4, the maximum size of each cache
system is assumed to be about 3 MB. There are five print jobs 1, 2,
3, 4, 5 that are issued by the agent cache system 302, and each
print job contains print data A, B, C, D, C, respectively, Each
data size is 1 MB, so the agent cache system 302 and the client
cache system 304 just hold three entries of print data.
[0048] The sequence of the print jobs issued by the agent cache
system 302 is 1, 2, 3, 4, 5. However, due to the latency in the
physical network 112, the sequence arriving at the client cache
system 304 is 3, 1, 2, 4, 5.
[0049] The initial states (empty) of the two cache systems are
shown at 400 and 402. At 404, the agent cache system 302 receives
print jobs 1, 2, and 3 in sequence from a virtual desktop; hashes
the print data of each print job to obtain hash values H.sub.A,
H.sub.B, and H.sub.C, and determines that these hash values are not
yet cached. So, the queue in the cache is populated respectively in
sequence with the hash values H.sub.A, H.sub.B, and H.sub.C, with
H.sub.A being at the rear node and H.sub.C being at the front node
of the cache. The agent cache system 302 also generates the
corresponding data structures for the print jobs J.sub.1, J.sub.2,
and J.sub.3, and sends them to the client cache system 304 in
sequence at 404. The data structures contain the hash values (H),
data size, and print data for each print job (e.g., {hash_value
data_size, data}={H.sub.A, 1 MB, A} etc.).
[0050] Due to network latency, the client cache system 304 receives
the print jobs in a different sequence (J.sub.3, J.sub.1, and
J.sub.2) than the sequence in which they were sent from the agent
cache system 302, and so the queue in the client cache system 304
is correspondingly populated with the print data in the sequence of
C, A, B (from the rear node to the front node) along with their
corresponding hash values, as shown at 406. Thus, while the agent
cache system 302 has the hash value H.sub.A at the rear node at
404, the client cache system 304 has a mismatched sequence having
the hash value H.sub.C at the rear node at 406.
[0051] At 408, the agent cache system 302 receives the print job 4
(J.sub.4); generates the hash value H.sub.D for the print job
J.sub.4; determines that the hash value H.sub.D is not yet cached,
and so stores the hash value H.sub.D in the front node of the
cache. Because the cache has a limit size of 3 MB, the least
recently used hash value H.sub.A at the rear node of the cache is
flushed out of the cache at 408. The agent cache system 302 then
generates the data structure {H.sub.D, 1 MB, D} for the print job
J.sub.4, and sends it to the client cache system 304.
[0052] At 410, the client cache system 304 receives the data
structure {H.sub.D, 1 MB, D} for the print job J.sub.4, and stores
the hash value H.sub.D and print data D at the front node of the
cache. As a result, the least recently used hash value H.sub.C and
corresponding print data C is flushed out from the rear node of the
cache at 410, thereby leaving a sequence of print data D, B, A and
their corresponding hash values, from the front node to the rear
node at 410.
[0053] At 412, the agent cache system 302 receives print job 5
(J.sub.5); hashes the print data C to generate the hash value
H.sub.C; and determines that the hash value H.sub.C is already
cached (in the middle node of the cache). Accordingly, the agent
cache system 302 generates a data structure {H.sub.C} that only
includes the hash value H.sub.C and does not include the actual
duplicative print data C since the print data C was previously sent
to the client cache system 304 (e.g., the agent cache system 302
performs deduplication at 412). The agent cache system 302 assumes
that the client cache system 304 still has the print data C cached
therein and that the client cache system 304 would then be able to
use the hash value H.sub.C provided via in the data structure
{H.sub.C} to locate/restore the print data C. It is noted herein
that in the cache management technique of FIG. 4, the contents of
the agent cache system 302 at 412 remains unchanged (e.g.,
maintains the same contents and sequence as that shown at 408) when
deduplication is performed. In other cache management techniques,
the duplicate hash value H.sub.C is written into the front node,
the previously cached hash value H.sub.C at the middle node is
deleted, and the hash value H.sub.D at the front node is shifted
downwards to the middle node.
[0054] Despite the assumption by the agent side that the print data
C is still cached at the client side, and as shown previously at
410, the client cache system 302 has actually previously removed
the print data C and its hash value H.sub.C from the cache. Thus,
when the client cache system 304 receives the print job J.sub.5
that specifies only the hash value H.sub.C, the client cache system
304 will have no previous record of this hash value H.sub.C and its
corresponding print data C. Accordingly, since the client cache
system 304 will therefore be unable to locate/restore the print
data C, the print job J.sub.5 will fail at 414.
[0055] VLRU Method
[0056] To address the foregoing and other issues with LRU
techniques, the various embodiments of the VLRU method described
herein, as a baseline, improve the chances for deduplicated print
data to be more consistently located/restored at the client side
for printing. Moreover, the VLRU method provides a high-performance
technique without introducing undue time-consuming complexity to
the cache management, thereby preserving a primary purpose (e.g.,
improving efficiency/performance) of caches. The caches at the
agent side and client side remain consistent/coherent with each
other, despite the fact that network latency may cause the
sequences at the two caches to be out-of-sequence with respect to
each other--the VLRU method does not require the two sequences in
the caches to be the same.
[0057] FIG. 5 is a diagram illustrating an example of a varied LRU
(VLRU) caching technique for a printing process for the client and
agent devices and printers of FIG. 2. In the example of FIG. 5 and
the subsequent figures, the caching at the agent side continues to
use an LRU caching technique similar to that described above with
respect to FIGS. 3 and 4 for purposes of adding and removing cache
entries, but with some differences (as will be described next) in
the contents/arrangement of the agent cache system 222 and the
content/format of the data structures sent to the client cache
system 212. The client side uses the VLRU caching technique for the
client cache system 212, in a manner that based on an operation
node (described next below) received from the agent side, the
deduped data at the agent side can be located/restored at the
client side for printing.
[0058] In the VLRU caching technique, the size of the cache at the
client cache system 212 is made greater than or equal to the size
of the cache at the agent cache system 222. That is, the client
cache system 212 can have more cache nodes (store more print data)
than the maximum number of cache nodes at the agent cache system
222, when appropriate and for a limited period of time. This
ensures that deduped print data can be recovered at the client side
and not lost. Moreover, a waiting list 500 is provided in the
client cache system 212 or elsewhere at the client side, for use in
storing hash values of print data that are being delayed/postponed
in their deletion, so as to again ensure that the print data is
available at the client side for restoration if/when deduplication
is performed at the agent side for that print data.
[0059] As shown in FIG. 5, an additional column (hit count) is
added to the agent cache system 222, in addition to columns for the
hash value H and data size S for each cache node (cache row). The
hit count represents a number of times that there is a hit for a
cached hash value of print data, when a deduplication is performed.
The hit count for newly inserted hash values of print data is zero,
and when there is a hit for the hash values when determining
whether to perform deduplication, the hit count is incremented by
one.
[0060] The format of data structures 502 sent from the agent side
to the client side (via the VDI connection 208) includes a flag and
information about the operation node. More specifically, the flag
identifies the three types of operations that may be performed on
the cache nodes at the agent cache system 222: updating node (e.g.,
deduplication), adding node (e.g., adding a new entry to the front
node), and deleting node (e.g., flushing a cache entry from the
rear node). As shown in FIG. 5, the data structures 502 include: a
DEDUPED flag and hash value for an updating node; a SAVE flag, hash
value, and print data for an adding node, along with a hash value
and hit count for a deleting node that is being deleted when the
adding node is added at the agent side.
[0061] The data structures 502 from the agent side are parsed at
the client side, such that the client cache system 212 includes,
for each cache node (row), columns for a hash value, hit count, add
count, and print data. The waiting list 500 includes, for each
cache node stored in the waiting list 500, columns for the hash
value, hit count, and a delete count.
[0062] FIGS. 6 and 7 illustrate how at least some of the features
of FIG. 5 are used. Reference is first made to FIG. 6, which is a
diagram illustrating a further example of the VLRU caching
technique for a printing process for the client and agent devices
and printers of FIG. 2. The example of FIG. 6 has some similar
assumptions/parameters as the previous example above in FIG. 4.
Specifically: the maximum size of the agent cache system 222 is
assumed to be about 3 MB; there are five print jobs 1, 2, 3, 4, 5
that are received by the agent cache system 222 from the virtual
desktop 126; each print job contains print data A, B, C, D, C,
respectively; and each data size is 1 MB, such that the agent cache
system 222 is able to hold three entries of print data. The client
cache system 212 in this example can hold more than three entries
(more than 3 MB of print data for a period of time. The sequence of
the print jobs sent by the agent cache system 222 is 1, 2, 3, 4, 5.
However, due to the latency in the physical network 112, the
sequence arriving at the client cache system 212 is 3, 1, 2, 4,
5.
[0063] The initial states (empty) of the two cache systems are
shown at 600 and 602. At 604, the agent cache system 222 receives
print jobs 1, 2, and 3 in sequence; hashes the print data of each
print job to obtain hash values H.sub.A, H.sub.B, and H.sub.C, and
determines that these hash values are not yet cached. So, the queue
in the cache is populated respectively in sequence with the hash
values H.sub.A, H.sub.B, and H.sub.C, with H.sub.A being at the
rear node and H.sub.C being at the front node of the cache. These
are thus adding nodes. The hit count for each cache node is 0 at
this stage. The agent cache system 222 also generates the
corresponding data structures for the print jobs J.sub.1, J.sub.2,
and J.sub.3 which include the SAVE flag for these adding nodes, and
sends the data structures to the client cache system 212 in
sequence at 604. The data structures contain the flag (SAVE), hash
values (H), and print data for each adding node in the print job
(e.g., {SAVE, H.sub.A, A} etc.).
[0064] Due to network latency, the client cache system 212 receives
the print jobs in a different sequence (J.sub.3, J.sub.1, and
J.sub.2) than that in which they were sent from the agent side, and
so the queue in the client cache system 212 is correspondingly
populated with the print data in the sequence of C, A, B (from the
rear node to the front node) along with their corresponding hash
values (0 each), as shown at 606. Moreover, since these are adding
nodes, the column for the add count is incremented to 1 at 606.
Thus and also as shown at 606, after print jobs 1, 2, and 3 are
completed at the client side, there is a mismatched sequence of
caches at the client side and agent side.
[0065] At 608, the agent cache system 222 receives the print job 4
(J.sub.4); generates the hash value H.sub.D for the print job
J.sub.4; determines that the hash value H.sub.D is not yet cached,
and so stores the hash value H.sub.D in the front node of the
cache. Because the cache has a limit size of 3 MB, the least
recently used hash value H.sub.A at the rear node of the cache is
flushed out of the cache. The agent cache system 222 then
generates, for the print job J.sub.4, the data structure {SAVE,
H.sub.D, D} for the adding node and {hash_value, hit count}
(specifically, {H.sub.A, 0}) for the deleting node, and sends this
to the client cache system 212.
[0066] At 610, the client cache system 212 receives the data
structure {SAVE, H.sub.D, D} {H.sub.A, 0} for the print job
J.sub.4, and stores the hash value H.sub.D, hit count, add count,
and print data D at the front node of the cache in accordance with
executing the SAVE operation for the print data A. Hence, the cache
now has four nodes for a period of time, and then later three nodes
after the delete operation is executed for the cache node for print
data A, as shown at 610 after print job 4 is completed. It is
therefore noted that the print data C (and is corresponding hash
value) was not flushed from the cache at 610, since the cache node
for print data A was deleted.
[0067] At 612, the agent cache system 222 receives print job 5
(J.sub.5); hashes the print data C to generate the hash value
H.sub.C; and determines that the hash value H.sub.C is already
cached (in the middle node of the cache). Accordingly, the agent
cache system 612 generates a data structure {DEDUPED, H.sub.C} that
only includes the hash value H.sub.C and does not include the
actual duplicative print data C since the print data C was
previously sent to the client cache system 212 (e.g., the agent
cache system 222 performs deduplication at 612). The agent cache
system 222 also increments the hit count for the hash value H.sub.C
from 0 to 1 at 612. The client cache system 614 receives the data
structure {DEDUPED, H.sub.C} at 614, and is able to successfully
use the hash value H.sub.C to locate the print data C at the rear
node of the cache. Thus, the print data C can thereafter be sent to
the physical printer(s) for printing.
[0068] Reference is made next to FIG. 7, which is a diagram
illustrating another example of the VLRU caching technique for a
printing process for the client and agent devices and printers of
FIG. 2. More specifically, FIG. 7 shows how the waiting list 500
(denoted as W.sub.I) may be used to ensure that print data
deduplicated at the agent side remains available at the client
side.
[0069] In the example of FIG. 7: the maximum size of the agent
cache system 222 is assumed to be about 3 MB; there are five print
jobs 1, 2, 3, 4, 5 that are received by the agent cache system 222
from the virtual desktop 126; each print job contains print data B,
C, D, E, F, respectively; and each data size is 1 MB, such that the
agent cache system 222 is able to hold three entries of print data.
The client cache system 212 in this example can hold more than
three entries (more than 3 MB of print data) for a period of time.
The sequence of the print jobs sent by the agent cache system 222
is 1, 2, 3, 4, 5. However, due to the latency in the physical
network 112, the sequence arriving at the client cache system 212
is 4, 5, 1, 2, 3.
[0070] The initial cache states (entries at each cache node) of the
two cache systems are shown at 700 and 702, which correspond to the
cache states at the end of the printing process previously depicted
in FIG. 6. At 704, the agent cache system 222 receives print jobs
1, 2, and 3 in sequence; hashes the print data of each print job to
obtain respective hash values H.sub.B, H.sub.C, and H.sub.D, and
determines that these hash values are already cached. That is,
there is a cache hit for each of these hash values. Hence, their
respective hit counts are incremented by 1 at 704 (e.g., the hit
count for H.sub.B is incremented from 0 to 1, the hit count for
H.sub.C is incremented from 1 to 2, etc.). Because the hash values
are found in the cache, the agent cache system 222 does not need to
resend the same corresponding print data to the client side (e.g.,
performs deduplication) and instead generates data structures
corresponding to updating nodes, in accordance with the format of
the data structure 502 shown in FIG. 5. Hence, the generated data
structures for the three updating nodes are: {DEDUPED, H.sub.B},
{DEDUPED, H.sub.C}, and {DEDUPED, H.sub.D}, and these are sent to
the client side in this sequence.
[0071] Next at 706, the agent cache system 222 determines that the
hash value H.sub.E for print job 4 does not exist in the cache. As
such, the hash value H.sub.E and its hop count (0) form an adding
node that is written to the front node of the cache at 706. The
hash value H.sub.B that was at the rear node at 704 is thus flushed
(e.g., becomes a deleting node) at 706 in order to make room in the
cache for the adding node. The agent cache system 222 then
generates the appropriate data structure to send to the client
side, so as to inform the client side of the adding node and the
corresponding deleting node: {SAVE, H.sub.E, E} {H.sub.B, 1}.
[0072] A similar process occurs next at 708, wherein the agent
cache system 222 determines that the hash value H.sub.F for print
job 5 does not exist in the cache. As such, the hash value H.sub.F
and its hop count (0) form an adding node that is written to the
front node of the cache at 708. The hash value H.sub.C that was at
the rear node at 706 is thus flushed (e.g., becomes a deleting
node) at 708 in order to make room in the cache for the adding
node. The agent cache system 222 then generates the appropriate
data structure to send to the client side, so as to inform the
client side of the adding node and the corresponding deleting node:
{SAVE, H.sub.F, F} {H.sub.C, 2}.
[0073] Due to latency in the physical network 112, the above data
structures do not arrive at the client side in the same sequence in
which they were sent from the agent side. That is, the sequence
arriving at the client side is print jobs 4, 5, 1, 2, 3, instead of
print jobs 1, 2, 3, 4, 5.
[0074] Print job 4 is received first at 710 at the client side,
with the data structure {SAVE, H.sub.E, E} {H.sub.B, 1}. A cache
node (adding node) is created at the front node of the cache to
store the hash value H.sub.E, the hit count 0, and the print data
E, as well as adding 1 to the add count column to indicate that
this is a newly added cache node. There are thus four cache nodes
at 710, after the completion of print job 4 to print data E. The
deleting node (corresponding to {H.sub.B, 1}) is not yet deleted
from the cache and is instead placed in the waiting list W.sub.I at
710, with the delete count set to 1 and the hit count in the
waiting list W.sub.I also at 1 (shown at 711). Note here that the
hit count for the hash value H.sub.B remains at 0 in the cache.
[0075] Print job 5 is received next at 712 at the client side, with
the data structure {SAVE, H.sub.F, F} {H.sub.C, 2}. A cache node
(adding node) is created at the front node of the cache to store
the hash value H.sub.F, the hit count 0, and the print data F, as
well as adding 1 to the add count column to indicate that this is a
newly added cache node. There are thus now five cache nodes at 712,
after the completion of print job 5 to print data F. The deleting
node (corresponding to {H.sub.C, 2}) is not yet deleted from the
cache and is instead placed in the waiting list W.sub.I at 712,
with the delete count set to 1 and the hit count in the waiting
list W.sub.I at 2 (shown at 713). Note here that the hit count for
the hash value H.sub.C remains at 1 in the cache.
[0076] Print job 1 is received next at 714 at the client side, with
the data structure {DEDUPED, H.sub.B}. As a result, the hit count
for the hash value H.sub.B is incremented (shown at 715) from 0 to
1 in the cache, thereby matching the hit count 1 for the hash value
H.sub.B in the waiting list W.sub.I (and also matching delete and
add counts that are both at 1), which are conditions that trigger
deletion of hash value H.sub.B from the cache and waiting list
W.sub.I. The print data B is printed to complete print job 1 at
714, and the cache is updated (shown at 716) to execute the delete
operation previously received at 710, thereby removing the hash
value H.sub.B from the cache and waiting list W.sub.I at 714.
[0077] A similar process is performed next at 718, when print job 2
is received at the client side, with the data structure {DEDUPED,
H.sub.C}. The hit count for the hash value H.sub.C is incremented
(shown at 719) from 1 to 2 in the cache, thereby matching the hit
count 2 for the hash value H.sub.C in the waiting list W.sub.I (and
also matching delete and add counts that are both at 1), which are
conditions that trigger deletion of hash value H.sub.C from the
cache and waiting list W.sub.I. The print data C is printed to
complete print job 2 at 718, and the cache is updated (shown at
720) to execute the delete operation previously received at 712,
thereby removing the hash value H.sub.C from the cache and waiting
list W.sub.I at 718. The wait list W.sub.I is empty at this point
(e.g., no more entries awaiting deletion).
[0078] Print job 3 is received next at 722 at the client side, with
the data structure {DEDUPED, H.sub.D}. The hit count for the hash
value H.sub.D is updated from 0 to 1 at 722, and the print data D
is located and sent to the physical printer for printing, thereby
completing print job 3 at 722.
[0079] FIG. 8 is a flowchart of an example method 800 to perform
the VLRU caching technique in the virtualized computing environment
100 of FIG. 1, such as the VLRU caching technique performed in the
previous FIGS. 5-7. Example method 800 may include one or more
operations, functions, or actions illustrated by one or more
blocks, such as blocks 802 to 816. The various blocks of the method
800 and/or of any other process(es) described herein may be
combined into fewer blocks, divided into additional blocks,
supplemented with further blocks, and/or eliminated based upon the
desired implementation. In one embodiment, the operations of the
method 800 and/or of any other process(es) described herein may be
performed in a pipelined sequential manner. In other embodiments,
some operations may be performed out-of-order, in parallel,
etc.
[0080] According to one embodiment, the method 800 may be performed
by the user device 146 and its client-side elements shown in FIGS.
2 and 5-7, in cooperation with the agent-side elements shown in
FIGS. 2 and 5-7. In other embodiments, various other elements in a
computing environment may perform, individually or cooperatively,
the various operations of the method 800.
[0081] At a block 802, the client cache system 212 receives a print
job J from the agent. The print job includes a data structure like
shown in FIG. 5 that species at least one type of operation to be
performed for a cache node at the client, a hash value
corresponding to print data at the cache node, and/or other
information (such as hit count).
[0082] The block 802 may be followed by a block 804 wherein the
client cache system 212 reads the data structure in the print job
and determines whether the data structure specifies at least one of
an add (SAVE), delete, or update (DEDUPED) operation. If the
operation is determined to be a delete operation at a block 806,
the deletion of the cache node specified in the data structure is
postponed. For instance, the hash value (and its accompanying data
such as the hit count and delete count) are stored in the waiting
list 500, so as to enable the client to subsequently use the hash
value to locate the print data in the cache for printing (if
another print job is later received that requires the printing of
that print data).
[0083] The block 806 may be followed by a block 808 wherein the
client cache system 212 receives another print job having another
data structure that species an update operation. For example, this
print job provides the hash value of print data that has been
deduplicated at the agent. As such, the client cache system 212 now
has to use (at a block 810) that hash value to attempt to
locate/restore the print data for printing at the physical
printer(s) at the client side.
[0084] Because the client cache system 212 has postponed the
deletion of the print data (back at the block 806), the client
cache system 212 is able to successfully use the hash value at the
block 810 to locate/restore the print data. At a block 812, the
client cache system 212 sends the print data to the physical
printer(s) for printing.
[0085] The block 812 may be followed by a block 814 wherein the
client cache system 212 executes the delete operation (received at
the block 802) in order to delete the cache node from either or
both the cache or the waiting list 500, if one or more conditions
are met. The method 800 then proceeds to block 816 so as to return
to the block 802 to await the next print job(s). Further details of
the update operation, add operation, and delete operation, and
applicable conditions for their execution, as explained for FIG. 8,
will be provided next with respect to FIGS. 9-11.
[0086] Specifically, FIG. 9 is a flowchart of an example method 900
associated with an updating node (deduplication) for the VLRU
caching technique of FIG. 8, and which may be performed by the
client cache system 212 at the client side. At a block 902, the
client cache system 212 receives a data structure from the agent,
for example in the form of {DEDUPED, H.sub.i} for a cache node at
the agent side having a hash value H.sub.i cached therein and for
which the agent has sent only the hash value (and not the print
data) due to deduplication performed at the agent.
[0087] At a block 904, the client cache system 212 checks whether
there a cache node N.sub.i exists in its cache that contains the
hash value H.sub.i. If the cache node N.sub.i does not exist ("NO"
at the block 904), then the client cache system 212 waits for the
cache node N.sub.i (the print data) to arrive (via an adding node
instruction from the agent side) at a block 906.
[0088] If the cache node N.sub.i does exist in the cache ("YES" at
the block 904), then the method 900 moves to a block 908 wherein
the hit count for the cache node is incremented by 1 in the cache,
such as shown at 715 and 719 in FIG. 7. Next at a block 910, the
client cache system 212 checks the waiting list W.sub.I to
determine whether a cache node N.sub.j having the hash value
H.sub.i exists in the waiting list W.sub.I. If the cache node
N.sub.j does not exist in the waiting list W.sub.I ("NO" at the
block 910), then the method 900 proceeds to a block 912, wherein
the print data at the cache node N.sub.i is sent to the physical
printer for printing and the method 900 ends.
[0089] On the other hand, if the cache node N.sub.j is determined
to exist in the waiting list W.sub.I ("YES" at the block 910), then
the method 900 proceeds to a block 914 to evaluate whether one or
more conditions are met. For example at the block 914, the client
cache system 212 determines (1) whether the hit count for the cache
node N.sub.j in the waiting list W.sub.I is equal to the hit count
for the cache node N.sub.i in the cache, and (2) whether the delete
count for the cache node N.sub.j in the waiting list W.sub.I is
equal to the add count for the cache node N.sub.i in the cache. If
these conditions are not met ("NO" at the block 914), then the
method 900 proceeds to the block 912, wherein the print data at the
cache node N.sub.i is sent to the physical printer for printing and
the method 900 ends.
[0090] However, if the conditions are met ("YES" at the block 914),
then the method 900 proceeds to a block 916 wherein the cache node
N.sub.i is deleted from the cache and the cache node N.sub.j is
deleted from the waiting list W.sub.I. The print data for the cache
node N.sub.i is sent to the physical printer and the method ends at
912.
[0091] Next are FIGS. 10 and 11 which may be viewed in tandem
regarding an add operation (to insert an adding node in a cache),
in combination with a delete operation (to correspondingly delete a
deleting node from a cache) which is performed if the cache is full
and not performed if the cache is not full.
[0092] Referring first to FIG. 10, which is a flowchart of an
example method 1000 associated with an adding node for the VLRU
caching technique of FIG. 8, the method 1000 may be performed by
the client cache system 212 at the client side. At a block 1002,
the client cache system 212 receives the data structure for an
adding node, with or without (represented by brackets [ ]) the data
structure for one or more deleting nodes in a deleting node set.
The data structure {H.sub.A, 0, A} provides the hash value H.sub.A,
the hit count 0 for a newly added cache node, and the print data
A.
[0093] At a block 1004, the client cache system 212 determines
whether a cache node N.sub.A having the print data A already exists
in the cache at the client side. If the cache node N.sub.A already
exists in the cache ("YES" at the block 1004), then the method 1000
proceeds to a block 1014 to increment (by 1) the add count in the
cache for the cache node N.sub.A. The method 1000 then proceeds to
a block 1016 to determine whether a cache node N.sub.j with the
hash value H.sub.A exists in the waiting list W.sub.I. If the cache
node N.sub.j does not exist in the waiting list W.sub.I ("NO" at
the block 1016), then the print data A at the cache node N.sub.A is
sent to the physical printer for printing (if there are no further
deletion operations to be performed), else the method 1000
continues in FIG. 11 with a method 1100 (flowchart continuity shown
at point A-A in FIG. 10) to perform the removal of deleting
nodes.
[0094] If, back at the block 1004, the client cache system 212
determines that the cache node N.sub.A does not exist in the cache
("NO" at the block 1004), then the method 1000 proceeds to a block
1006 to determine whether the cache node N.sub.A with the hash
value H.sub.A exists in the waiting list W.sub.I. If the cache node
N.sub.A with the hash value H.sub.A does not exist in the waiting
list W.sub.I ("NO" at the block 1004), then the cache node N.sub.A
is added to the cache at a block 1008, including the hash value
H.sub.A, the hit count 0, the add count 1, and the print data A.
Else, if the cache node N.sub.A with the hash value H.sub.A does
exist in the waiting list W.sub.I ("YES" at the block 1004), then
the method 1000 proceeds to a block 1010 to determine whether one
or more conditions are met.
[0095] For example at the block 1010, the client cache system 212
determines (1) whether the hit count for the cache node N.sub.A in
the waiting list W.sub.I is equal to 0, and (2) whether the delete
count for the cache node N.sub.A in the waiting list W.sub.I is
equal to 1. If these conditions are not met ("NO" at the block
1010), then the method 900 proceeds to point A-A for printing of
the print data A or deletion of deleting nodes (described in FIG.
11). If, however, these conditions are met ("YES" at the block
1010), then the method 1000 proceeds to a block 1012 to delete the
cache node N.sub.A in the waiting list W.sub.I, and the method 1000
proceeds to the point A-A for printing of the print data A or
deletion of deleting nodes (described in FIG. 11).
[0096] If, back at the block 1016, the client cache system 212
determines that the cache node N.sub.j with the hash value H.sub.A
exists in the waiting list W.sub.I ("YES" at the block 1016), then
the method 1000 proceeds to a block 1018 to determine whether one
or more conditions are met. For example at the block 1018, the
client cache system 212 determines (1) whether the hit count for
the cache node N.sub.j in the waiting list W.sub.I is equal to the
hit count for the cache node N.sub.A in the cache, and (2) whether
the delete count for the cache node N.sub.j in the waiting list
W.sub.I is equal to the add count for the cache node N.sub.A in the
cache. If these conditions are not met ("NO" at the block 1018),
then the method 1000 proceeds to point A-A to print the data A or
to execute deletion operations to delete deleting nodes (described
in FIG. 11). However, if the conditions are met ("YES" at the block
1018), then the method 1000 proceeds to a block 1020 wherein the
cache node N.sub.i is deleted from the cache and the cache node
N.sub.j is deleted from the waiting list W.sub.I, and then the
method 1000 proceeds to point A-A to print the data A or to execute
deletion operations to delete deleting nodes (described in FIG.
11).
[0097] Referring next to FIG. 11, which is a flowchart of an
example method 1100 associated with a deleting node for the VLRU
caching technique of FIG. 8 and which continues at point A-A from
FIG. 10, the method 1100 may be performed by the client cache
system 212 at the client side.
[0098] After the adding node is processed by the method 1000 shown
in FIG. 10, the method 1100 starts at block 1102 to go through each
deleting node N.sub.k, one by one, in the deleting nodes set
(contained in the data structure at the block 1002 in FIG. 10).
Each deleting node N.sub.k at the block 1102 includes a hash value
H.sub.k and a current hit count C.sub.k (e.g., {H.sub.k, C.sub.k})
as received from the agent.
[0099] At a block 1104, the client cache system 212 determines
whether the deleting node N.sub.k with a hash value H.sub.k exist
in the cache. If the deleting node N.sub.k exists in the cache
("YES" at the block 1104), then the method 1100 proceeds to a block
1106 to determine whether one or more conditions are met. For
example at the block 1106, the client cache system 212 determines
(1) whether the hit count for the deleting node N.sub.k in the
cache is equal to the hit count C.sub.k as received from the agent,
and (2) whether the add count for the deleting node N.sub.k in the
cache is equal to 1. If these conditions are met ("YES" at the
block 1106), then the method 1100 proceeds to a block 1108 to the
delete the deleting node N.sub.k from the cache.
[0100] However, if the conditions are not met ("NO" at the block
1106) or if the deleting node N.sub.k does not exist in the cache
("NO" back at the block 1104), then the method 1100 proceeds to a
block 1110 to postpone the deletion of the deleting node N.sub.k,
by first determining whether the deleting node N.sub.k exists in
the waiting list W.sub.I. If the deleting node N.sub.k does not
exist in the waiting list W.sub.I ("NO" at the block 1110), then
the method 1100 proceeds to a block 1112 wherein the deleting node
N.sub.k is added in the waiting list W.sub.I, specifically the hash
value, hit count as received from the agent, and the deleting count
of 1 are inserted as {H.sub.k, C.sub.k, 1} into the waiting list
W.sub.I at the block 1112. If, back at the block 1110, the deleting
node N.sub.k does exist in the waiting list W.sub.I ("YES" at the
block 1110), then the method 1100 proceeds to a block 1114, wherein
the delete count for the deleting node N.sub.k in the waiting list
W.sub.I is incremented by 1, and the hit count for the deleting
node N.sub.k in the waiting list W.sub.I is incremented so as to be
equal to the current hit count C.sub.k as received from the agent.
The method 1100 then proceeds to repeat the process the next
deleting node in the deleting node set, in accordance with the
blocks 1102-1114 above.
[0101] Computing Device
[0102] The above examples can be implemented by hardware (including
hardware logic circuitry), software or firmware or a combination
thereof. The above examples may be implemented by any suitable
computing device, computer system, etc. The computing device may
include processor(s), memory unit(s) and physical NIC(s) that may
communicate with each other via a communication bus, etc. The
computing device may include a non-transitory computer-readable
medium having stored thereon instructions or program code that, in
response to execution by the processor, cause the processor to
perform processes described herein with reference to FIGS. 1-11.
For example, computing devices capable of acting as agent-side host
devices or client-side user devices may be deployed in or otherwise
operate in conjunction with the virtualized computing environment
100.
[0103] The techniques introduced above can be implemented in
special-purpose hardwired circuitry, in software and/or firmware in
conjunction with programmable circuitry, or in a combination
thereof. Special-purpose hardwired circuitry may be in the form of,
for example, one or more application-specific integrated circuits
(ASICs), programmable logic devices (PLDs), field-programmable gate
arrays (FPGAs), and others. The term `processor` is to be
interpreted broadly to include a processing unit, ASIC, logic unit,
or programmable gate array etc.
[0104] Although examples of the present disclosure refer to
"virtual machines," it should be understood that a virtual machine
running within a host is merely one example of a "virtualized
computing instance" or "workload." A virtualized computing instance
may represent an addressable data compute node or isolated user
space instance. In practice, any suitable technology may be used to
provide isolated user space instances, not just hardware
virtualization. Other virtualized computing instances (VCIs) may
include containers (e.g., running on top of a host operating system
without the need for a hypervisor or separate operating system; or
implemented as an operating system level virtualization), virtual
private servers, client computers, etc. The virtual machines may
also be complete computation environments, containing virtual
equivalents of the hardware and system software components of a
physical computing system. Moreover, some embodiments may be
implemented in other types of computing environments (which may not
necessarily involve a virtualized computing environment), wherein
it would be beneficial to ensure that deduped data is available at
a client for printing.
[0105] The foregoing detailed description has set forth various
embodiments of the devices and/or processes via the use of block
diagrams, flowcharts, and/or examples. Insofar as such block
diagrams, flowcharts, and/or examples contain one or more functions
and/or operations, it will be understood that each function and/or
operation within such block diagrams, flowcharts, or examples can
be implemented, individually and/or collectively, by a wide range
of hardware, software, firmware, or any combination thereof.
[0106] Some aspects of the embodiments disclosed herein, in whole
or in part, can be equivalently implemented in integrated circuits,
as one or more computer programs running on one or more computers
(e.g., as one or more programs running on one or more computing
systems), as one or more programs running on one or more processors
(e.g., as one or more programs running on one or more
microprocessors), as firmware, or as virtually any combination
thereof, and that designing the circuitry and/or writing the code
for the software and or firmware are possible in light of this
disclosure.
[0107] Software and/or other instructions to implement the
techniques introduced here may be stored on a non-transitory
computer-readable storage medium and may be executed by one or more
general-purpose or special-purpose programmable microprocessors. A
"computer-readable storage medium", as the term is used herein,
includes any mechanism that provides (i.e., stores and/or
transmits) information in a form accessible by a machine (e.g., a
computer, network device, personal digital assistant (PDA), mobile
device, manufacturing tool, any device with a set of one or more
processors, etc.). A computer-readable storage medium may include
recordable/non recordable media (e.g., read-only memory (ROM),
random access memory (RAM), magnetic disk or optical storage media,
flash memory devices, etc.).
[0108] The drawings are only illustrations of an example, wherein
the units or procedure shown in the drawings are not necessarily
essential for implementing the present disclosure. The units in the
device in the examples can be arranged in the device in the
examples as described, or can be alternatively located in one or
more devices different from that in the examples. The units in the
examples described can be combined into one module or further
divided into a plurality of sub-units.
* * * * *